An improved solution for integrated array optics in quasi-opticalmm and submm receivers: the hybrid antenna

A dielectric lens antenna that is a special case of an extended hemispherical dielectric lens and is operated in the diffraction-limited regime is considered. The dielectric lens antenna is fed by a planar antenna that is mounted on the flat side of the dielectric lens antenna, using it as a substrate, and the combination is termed a hybrid antenna. Beam pattern and aperture efficiency measurements were made at millimeter and submillimeter wavelengths as a function of the extension of the hemispherical lens and of lens size. An optimum extension distance for which excellent beam patterns and simultaneously high aperture efficiencies can be achieved is found experimentally and numerically. At 115 GHz the aperture efficiency was measured to be (76±6)% for a diffraction-limited beam with sidelobes below -17 dB. Results for a single hybrid antenna with an integrated superconductor-insulator-superconductor (SIS) detector and a broadband matching structure at submillimeter wavelengths are presented. The hybrid antenna is space efficient in an array due to its high aperture efficiency, and is easily mass produced, thus being well suited for focal plane heterodyne receiver arrays     

A comparison among 1-, 3-, and 7-horn feeds for a 37-beam MBA

A very common multiple beam antenna (MBA) configuration consists of a collimating device illuminated by an array of feeds. The collimating device is usually a reflector or a lens. The feeds are usually horn antennas with a circular aperture. The reflector is usually offset-fed to eliminate aperture blockage; the lens is center fed. The antenna's feeds are excited to produce a finite number of beams, so as to provide contiguous coverage of the field of view. The designer is forced to minimize the angular spacing between adjacent beams in order to maximize the minimum gain over the antenna's field of view. On the other hand, the feed horn's aperture gain is maximized when the feed horn spacing and its aperture diameter are equal. This results in antenna efficiency of the order of 30% when a single feed horn is excited to produce a beam. When a cluster of 3 or 7 adjacent feed horns are excited to produce a single beam, antenna efficiency can be increased to 50%. When it is tolerable, several identical antenna apertures can be used to replace a single aperture configuration. In this case, each of M apertures produces approximately N/M beams of an MBA that produces N beams. Horns producing adjacent beams do not illuminate the same aperture. This permits the use of a much larger horn aperture for a given beam spacing. This results in reduced spillover, higher gain of each beam, and increased antenna efficiency of each aperture. This paper investigates the maximization of gain for several lens antennas. It shows that antenna gain is increased as its focal length is decreased. That is, a focal length-to-diameter ratio (F/D) less than 1 is preferred     

一种高效率的四脊喇叭馈源

以天线口径效率为目标,研究了四脊喇叭口径对馈源波束等化、波束宽度恒定和天线口径效率等性能的影响,得到了一种3∶1带宽高效率圆四脊喇叭馈源的设计。该馈源在整个频带内具有较低的电压驻波比,三个主平面的主极化方向图波束等化较好,-10d B波束宽度基本恒定,且天线口径效率达到55%以上。     

基于口面场方法的W波段高口面效率单脉冲卡塞格伦天线

本文提出来一种应用于直升机防撞雷达的高口面效率W波段单脉冲双反射面卡塞格伦天线。口面分析方法的提出解决了W波段反射面天线口面相位分布不均匀的缺陷,从而有效的提高了口面的利用效率。利用该方法,本文研究并制作了口径为135mm、焦距为40.5mm的W波段卡赛格伦天线,并且设计了由四个E面多缝隙电桥和四个四分之一波导波长延迟线级联构成的和差网络。经测试,该单脉冲天线在93GHz具有38.6dBi的和波束增益,相应的口面效率为54.7%;差波束的零深优于-22dB,副瓣电平小于-18dB。测试结果与基于口面分析方法的仿真结果吻合,从而证明了本文所研究天线可以应用于高口面效率的W波段单脉冲系统中。     

Scalar horn with shaped lens improves Cassegrain efficiency

It is shown that the aperture efficiency of a classical Cassegrain antenna can be considerably improved if the radiation pattern of the feed is optimally shaped. The corresponding optimum field distribution Over the aperture of the feed consists of a circular main lobe which is surrounded by concentric sidelobe rings. This optimum field distribution with one sidelobe ring included is realized by shaping of a dielectric lens which is positioned in the aperture of a corrugated horn antenna. The design can provide a theoretical aperture efficiency of 90.5 percent when subreflector diffraction and aperture shadowing are neglected, i.e., an improvement of 0.4 dB compared to an optimum conventional feed. Measurements of a model at 22.8 GHz gave a practical result of 85.6 percent. If the model is used to feed a 30 m radiotelescope the overall antenna efficiency becomes about 71 percent.     

高增益高效率的Fabry-Perot谐振腔天线研究

提出了一种采用非均匀频率选择表面（frequency selective surface, FSS）盖板以及非均匀电磁带隙（electromagnetic band gap, EBG）结构反射地板的高增益Fabry-Perot（F-P）谐振腔天线. 基于漏波理论模型,针对大口径F-P谐振腔天线设计非均匀的FSS盖板和EBG反射地板,控制衰减常数α和相位常数β,改善了口径场上幅度相位分布的均匀性,并抑制了非谐振频率时天线辐射性能的恶化,实现高增益和高口径效率的同时,保证了天线的工作带宽. 所提出的圆形F-P谐振腔天线直径为6.6λ₀,仿真增益为24.6 dBi,口径效率达67.9%,阻抗带宽为4.1%,3 dB增益带宽为3.7%;实测增益为23.9 dBi,口径效率达56.9%. 由于对口径场均匀性的设计,该天线克服了传统F-P谐振腔天线的口径效率和增益间的相互限制.     

A note on the coupling efficiency between an antenna and a Gaussian beam

In this communication a note on the coupling efficiency between an antenna and a Gaussian beam is presented. The calculations of the coupling efficiency from both methods, a nomorlized inner product between the antenna radiation pattern and the Gaussian-beam pattern or alternatively, between the electric field at the antenna aperture and a two-dimensional field representation of a Gaussian beam, are compared for different aperture size in wavelength. How a correct solution can be gotten is stated.     

试验天线对雷达罩传输效率的影响及分析

在雷达罩电性能测试过程中,需要用到试验天线,试验天线的类型、极化方式和口径尺寸对雷达罩电性能测试结果有一定影响。文中对试验天线口径尺寸对雷达罩传输效率的影响程度进行了仿真计算,通过对比测试验证了仿真计算的正确性。计算和测试结果表明:当试验天线与装机天线口径尺寸差别不大时,试验天线口径尺寸对传输效率的影响较小。在工程实践中,当无法得到装机天线时,可以用类型相同、极化方式相同、口径相近的天线作为试验天线,以完成传输效率的测试。     

高效率低旁瓣天线口面场分布函数研究

在赋形双反射面天线中,口面场分布函数对天线电气性能起到至关重要的作用。口面场分布函数妆接影响天线的增益和近角旁瓣。在传统卫星通信地面站中,要求天线第一旁瓣电平在-14dB以下,口面利用率在90%左右,而射电天文望远镜要求天线第一旁瓣电平小于-20dB,口面利用率要求在85%以上。研究并给出了一种整个口面能量均匀分布而外边缘低锥销的口面场分布函数,可以满足高增益,低旁瓣的要求。     

On the efficiency and radiation patterns of mismatched shaped Cassegrainian antenna systems

Calculations are carried out with regard to the aperture illumination efficiency, spillover efficiency, and blockage efficiency of a shaped Cassegrainian antenna system whose feed pattern is not similar to that for which the antenna was designed. It appears that a maximum overall efficiency may be expected for antenna systems with a feed pattern having a slightly narrower beamwidth than those for which the systems were originally designed. It is further proved that the radiation pattern of mismatched systems is very unfavorable in the case of the beamwidth of the feed pattern being wider than the beamwidth of the feed pattern for which the system was designed. This is due to overillumination of the edges.     

Scattered and absorbed powers in receiving antennas

This paper discusses the amount of power, which is scattered and absorbed by a receiving antenna and in particular, whether an antenna can absorb the entire power incident upon it. The absorbed and scattered power from dipole arrays in either free space, or over ground plane is considered. By defining a suitable "aperture efficiency" for the receiving case, a dipole array without a ground plane can best absorb half of the incident power (scattering the rest), while an array over a ground plane can absorb all of the incident power. It is shown how aperture efficiency varies with load impedance, which is of practical interest for array designers.     

Preliminary announcement of an 85 percent efficient reflector antenna

This communication is our preliminary announcement and claim for achievement of 85 percent aperture efficiency using a dual reflector antenna. We are aware of no other reflector antenna having such aperture efficiency, and we invite the antenna community to comment, critique, or inform us of equal or better claims. A full report will be forthcoming; this brief note will supply only pertinent highlights.     

Analysis of active surface reflector antenna for a large millimeterwave radio telescope

The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas     

L波段高功率线极化径向线阵列天线优化设计

针对L波段高功率线极化径向线阵列天线进行了优化设计.分析了影响阵列天线口径效率的因素,通过三种途径优化了口径效率;同时对单元天线进行适当的优化,减小了阵列天线的反射,提高了阵列天线的整体性能,使其更好地应用于实际.模拟结果表明:经过改进后,阵列天线的口径效率从原来的50.57%提高到85.1%,中心频率上的反射系数降为0.1146,且在513兆赫兹的频率范围内反射系数都小于0.2.     

Integral equation analysis of a sheet impedance coated window slotantenna

Presents an integral equation and method of moments analysis of a window slot antenna. The antenna is modeled by a sheet admittance coated rectangular aperture in an infinite ground plane. It is shown that the sheet admittance coated aperture is complementary to a sheet impedance plate, which permits the window slot antenna to be analyzed with existing computer programs. Numerical results are compared with measurements for input impedance and radiation efficiency     

Gaussian beam techniques for illuminating reflector antennas

Simple design procedures are presented for use when a Gaussian beam is used to illuminate a classical reflector antenna. Displacement of the location of the beamwaist toward the focusing element in the case of electrically small antennas where the aperture is in the near field of the feed was calculated together with modification of the required beamwaist radius. Dual reflector antennas were discussed and design procedures appropriate for systems with large and small focal length to diameter ratio developed. Cases where a reflector or subreflector is electrically small, or in the near field of a feed, are readily treated. For elliptical beam antennas, a simple illumination system using only a scalar horn and a single cylindrical lens can generally be found; this has no ray optics analogue. A configuration of this type is discussed, with a practical case study of a 28-by-80-λ elliptical Cassegrain antenna operating at a wavelength of 3 mm. The design process for designing the feed system is discussed in detail. Despite the small size and relatively large aperture blockage, an aperture efficiency of 0.48 was measured, which compared quite well with the expected efficiency of 0.53, thus verifying the validity of the Gaussian beam design approach     

Optimization of aperture illumination for radio wave power transmission

A basic design of an aperture illumination of antennas used for radio wave power transmission is presented. In the power transmission using microwave such as solar power satellite, not only the transmission efficiency, but also the transmitting power capacity allowed by the necessary electromagnetic environment is a very important factor for realization. In this paper the circular antenna aperture illumination is optimized in order to give the maximum transmission efficiency with the constraint on the radiation levels at the edge of the receiving aperture and at the radiation peaks of the subsequent sidelobes. This constrained optimization problem is solved by successive use of the sequential unconstrained minimization techniques (SUMT method). The maximum transmission efficiency and receivable average power density are obtained for various constrained levels of the spilled radiation, and are compared with the values in the unconstrained case.     

Multiple beam feed networks using an even number of beam ports

An aperture illumination compatible with the use of an even number of adjacent beam ports in a multiple beam feed network is discussed. The antenna pattern characteristics of near-in sidelobe levels, half-power beamwidth, aperture efficiency, and feed network loss are evaluated. Maximization of the available antenna gain at adjacent beam crossover points is shown to be possible for either sequential or simultaneons operation of a receiving system. The results presented indicate that lossy feed networks are quite suitable for certain array antenna applications.     

Optimum aperture monopulse excitations

A unified formulation of the optimization of monopulse antenna performance indices for a specified sidelobe envelope function and/or specified nulls of the pattern is presented. The performance indices considered are beam efficiency, gain factor, and angular sensitivity factor of rectangular and circular apertures. The unconstrained optimization of beam efficiency result in an integral equation, the solutions of which are prolate spheroidal wave functions for rectangular aperture and hyperspheroidal wave functions for circular aperture. These functions reduce, respectively, to Legendre and Zernike polynomials in the case of gain factor and angular sensitivity factor. The double orthogonality properties of these eigenfunctions are used for constrained optimization. The results obtained by this technique for the near-in sidelobes constrained at a uniform level are shown to be in agreement with the earlier works. The method is applicable for other aperture surfaces such as elliptical, ellipsoidal, and spherical.     

反射面天线焦面场采样研究与相控阵馈源设计

为了设计高性能的相控阵馈源(phased array feed,PAF),通过反射面天线焦面场最优采样的研究,给出了PAF参数与天线口径效率之间的关系,总结了PAF的最优采样范围和单元间距,导出了PAF单元数量的计算公式.给出了一个9 m天线的PAF设计实例和性能分析,在4～7 GHz频率范围内,扫描范围为±3°时,天...